Last night, I discovered that you can make corn on the cob in about 5 minutes, which is so cool. You can also backup your MongoDB database in about 5 minutes (depending on size!), so I figured I’d combine the two.
You’ll need:
- 1 MongoDB server you want to back up
- 1 external drive for the backup
- 2 ears of unshucked corn
- 2 tablespoons of butter
- 4 tablespoons of grated Parmesan cheese
- 1/2 teaspoon of cayenne pepper
Directions:
- Cook the ears of corn in the microwave for 4 minutes (in their husks) on a damp paper towel.
- Start a MongoDB shell and run:
> use admin > db.runCommand({"fsync" : 1, "lock" : 1}) { "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock", "ok" : 1 }
This flushes everything to disk and prevents more writes from happening. If you’re in production, you should do this on a slave (so you don’t prevent people from writing to the master). When you unlock it, the slave will start doing writes again and catch up with the master.
- Copy your database files to external storage:
$ cp -R /data/db /mnt/usb/backup
- Your corn is probably done now. Take it out of the microwave and cover it in a towel to let it cool.
- In your database shell, run:
> db.$cmd.sys.unlock.findOne() { "ok" : 1, "info" : "unlock requested" }
- If it’s cool enough, shuck your corn (the husks and silk should come off very easily, everything practically fell off for me).
- Roll the corn around in butter until it’s nice and coated. Then cover it with Parmesan cheese and sprinkle a little cayenne over it.
- Optional: eat corn over your laptop, safe in the knowledge that you have a recent backup.
I got this recipe from Tabla (the corn, not the database backup). There was a BBQ day at Madison Square Park and they’re too ritzy to serve BBQ, so they made this. It is really good.
Microwave mexican corn! Next time I see corn at the Journal Square farmers market I will make some for my coworkers. Personally I prefer text dumps for my database backups because they are more versatile, but this is a good alternative, and something I'll use when my mongo dbs get to big for the overhead of mongodump.
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You've inspired me to write a blog post, Thanksgiving dinner and compiling mongo on a netbook in 4 hours.
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Once you have the database locked up, you can pretty much do whatever type of dump you want on it (mongodump, mongoexport, etc), I just did cp -R because it's easy and everyone knows it 🙂
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Yup, same with my MacBook Air. The last couple of days have been crazy, too — ~50 commits in the last 12 hours — so I have to keep recompiling!
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Wait, if I do a mongodump without –dbpath, do I still have to issue the lock command or does mongodump do that for me? If I have to issue the locks, I gotta go modify some batch files, and more importantly file me some bugs and rouse some rabble.
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Yes, you still have to issue the locks! Change those batch files and rouse the rabble!
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Consider the rabble roused http://jira.mongodb.org/browse/SERVER-1588.Monday I shall update some batch files.
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Does it work the same way with replica sets? Or would I need to shutdown the replica and copy the files before bringing it back up?
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You can do the same thing with a replica set. Each member of a replica set is also an independent mongod, so connect to a secondary, fsync and lock it, and make a copy of the files.
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It wont work for the shards.. you need the backup for configs and for all shard members..
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